Device in a filter sector for a rotating filter disc

ABSTRACT

A filter sector for a rotating filter disc has filtrate conduits for filtrate resulting from filtration which is discharged at the more narrow end of the filter sector. The filtrate conduits are outwardly defined by a filtrating layer permeable to the filtrate. The filter sector has at least one element provided with a profiling forming the filtrate conduit. The profiled element itself forms the filtrating layer because the profiled element has a perforation permeable to the filtrate.

FIELD OF THE INVENTION AND PRIOR ART

This invention is related to a device in a filter sector for a rotatingfilter disc, said filter sector having filtrate conduits intended forfiltrate resulting from filtration, said filtrate being discharged atthe more narrow end of the filter sector, said filtrate conduits beingoutwards defined by a filtrating layer permeable to said filtrate andsaid filter sector comprising at least one element provided with aprofiling forming said filtrate conduits.

BACKGROUND AND SUMMARY OF THE INVENTION

The device according to the invention may be utilized in connection withany liquid medium, comprising various liquids, suspensions, etccontaining constituents desired to be filtered away. Even if theinvention in no way is restricted thereto, a preferred application ofthe invention is in connection with dewatering of fibre suspensions. Asfibres, cellulose fibres are primarily in view.

A device of the above mentioned type is previously known from theSwedish patent 8903128-0 (465 658). The filtrating layer is in the knowndevice formed by a fibre cloth surrounding said at least one profiledelement. When the filtrate comes through the filter cloth, it will thusenter into filtrate conduits formed between the filter cloth and said atleast one profiled element. The filter cloth will thereby extendsubstantially flat over the peaks of the profilings of said at least oneprofiled element.

A disadvantage with such a filter cloth is that it is proportionatelysensitive and may thus easily be damaged, which necessitates operationbreakdowns in order to change filter cloths. The active surface of thefilter is further limited to substantially the sum of the surface ofboth sides of the filter sector due to the fact that the filter clothextends substantially flat on these sides.

The object of this invention is to further develop the device accordingto the prior art so as to simplify the embodiment of the filter sectorand at the same time create the necessary conditions for increasedfiltration capacity of the filter sector.

This object is according to the invention achieved by that the profiledelement itself forms the filtrating layer as a consequence of that saidprofiled element has a perforation permeable to said filtrate.

Thus, the need for a filter cloth will completely be eliminated; said atleast one profiled element will itself by way of its perforation fulfilthe filtrating function, which according to prior art was taking care ofby means of a separate filter cloth. Further, a capacity increase isachieved by the solution according to the invention by means of that thetotal filter surface on the filter sector is increased as a consequenceof the profiling of said at least one element.

The circumstance that the filtrating layer according to the inventionthus will be formed by a profiled layer has surprisingly for a manskilled in the art turned out to not involve any difficulties regardingreleasing material filtered away and deposited on the filter sector.This release takes in the preferred case place by means of water jetnozzles.

The projections/recesses formed by the profiling may have the characterof elongated ridges/valleys, but may also be more point-like, forexample in the form of bulges.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the enclosed drawings a more specific description ofembodiment examples of the invention will follow hereunder.

In the drawings:

FIG. 1 is a diagrammatical, partly cut view of a so called disc filterseen along the axis of rotation of the filter,

FIG. 2 is a view from one side of a filter sector comprised in a filterdisc of the disc filter,

FIG. 3 is a view of the filter sector according to FIG. 2 seen from itsopposite side,

FIG. 4 is a cut illustrating the forming at IV--IV in FIG. 2,

FIG. 5 is a cut at V--V in FIG. 2,

FIG. 6 is a cut at VI--VI in FIG. 2,

FIG. 7 is a cut along the line VII--VII in FIG. 2,

FIG. 8 is a cut along the line VIII--VIII in FIG. 2,

FIG. 9 is a cut along the line VI--VI in FIG. 2 showing a somewhatmodified embodiment,

FIG. 10 is a view similar to FIG. 2 of a filter sector according to analternative embodiment,

FIG. 11 is a view of said filter sector according to FIG. 10 seen fromthe opposite side, and

FIG. 12 is a cut along the line XII--XII in FIG. 10.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The device according to the invention will hereinafter be described asapplied for dewatering of cellulose fibre pulp.

The disc filter illustrated in FIG. 1 comprises a container, which isgenerally denoted 1 and which has an inlet 2 for the fibre suspension. Arotor, which is generally denoted 3 is rotatably arranged in thecontainer 1. This rotor comprises an inner corelike rotor part 4 and anumber of filter discs 5 orientated transversely to the geometrical axisof the inner rotor part 4. This geometrical axis coincides with the axisof rotation of the rotor. The filter discs 5 are orientatedsubstantially perpendicularly to the axis of rotation of the rotor sothat the single filter disc 5 will extend in an annular configurationaround the inner rotor part 4. This annular configuration is morespecifically divided into a number of filter sectors 6. Each of thesefilter sectors 6 has inner filtrate conduits, which are outwardlydefined by a filtrating layer permeable to the filtrate. It is in FIG.1, regarding one of these filter sectors, illustrated by means of closelines intersecting each other, that the filter sector in question isintended to have an outer permeable filtrating layer.

It appears from FIG. 1 that each single filter sector 6 has a pipe-likeconduit section 7 for transferring the filtrate, i.e. the filtratedwater, from the filtrate conduits in the filtrating part of the filtersector into a respective filtrate conduit 8 in the rotor part 4 throughan opening 9 in a covering 10 of the rotor part 4, which opening isarranged for the filter sector in question.

The disc filter comprises means 11 for releasing fibre material, whichhas been filtered away, and which is deposited on the filter discs.These releasing means 11 are here formed by spray nozzles arranged toseparate, by means of suitable spraying of water or other liquid, themat of material, which has been filtered away, from the filter sectorsas they rotate by. A shaft-like receiver 12, in which released materialis intended to drop, is arranged between two neighbouring filter discs.The different shafts may be connected by means of an under conduit,which extends along the axis of rotation of the filter rotor, in whichconduit means 13, for example a transportation screw, may be arrangedfor removal of the material, which has been filtered away.

The pipe-like conduit sections 7 form a spoke configuration between thefilter sectors 6 and the inner rotor part 4, i.e. there are open spacesbetween these individual spokes. These open spaces make it possible forthe fibre suspension to distribute itself uniformly along the length ofthe container 1. Besides, the fibre suspension may of course distributeitself within the container 1 through the slots occurring radiallyoutwardly of the peripheries of the filter discs 5 and the inside of thecontainer 1. The inner rotor part 4 has the character of a rotatablyjournalled centre shaft.

The filtrate conduits 8 within the central shaft 4 have the character ofsector-shaped spaces mutually separated by means of substantiallyradially orientated partition walls 12 extending along the entire lengthof the centre shaft 4. The centre shaft 4 has a tubular core 43, againstthe mantle of which the partition walls 12 adjoin tightly.

It appears from FIG. 1 how two outlets 14, 15 are provided for filtrate.The outlet 14 is intended for a pre-filtrate (cloudy filtrate) whereasthe outlet 15 is intended for a clear filtrate. These outlets 14, 15 arearranged on one end of the centre shaft 4 and so stationary disposed ina well known way that the pre-filtrate outlet communicates with thefiltrate conduits 8 belonging to the filter sectors 6, which after beingreleased from mats of material filtered away move down into thesuspension prevailing in the container 1, the level of which suspensionis denoted at 16 and is for example situated just above the centre shaft4. The device may thereby be of the kind that the water flowing into thefilter sectors 6 by influence of gravitation may exit in thepre-filtrate outlet 14 when the filter sectors move down into thesuspension and have moved a distance down into the suspension. Thefiltrate conduits 8 will thereafter be connected to the clear filtrateoutlet 15, which advantageously may be supplied with a negative pressurein order to achieve suction of the filtrate into and through the filtersectors. When the filter sectors on the other side of the container thenmove out of the suspension, air will be suctioned through the filtersectors and through the mats of material, which has been filtered away,said mats being located on the filter sectors, so that a drying effectto a certain extent arises before the mats of material are finallyremoved from the filter sectors with the aid of the means 11.Furthermore, the disc filter has means 17 for cleaning the filtersectors after they are released from deposited fibre material with theaid of the removal means 11. In order to avoid undesired deposits offibre material on the walls limiting the shaft 12, means 18 may beprovided in order to spray water on one or several of said walls.

The detailed structure of a single filter sector will now be describedin more detail referring to FIGS. 2-9. The illustrated filter sector 6has filtrate conduits 19, 20 for filtrate achieved by filtration, whichis deposited at the more narrow end of the filter sector to thepipe-like conduit section 7, which is intended to release the filtrateat its radially inner end to a completing filtrate conduit 8 within therotor shaft 4.

These filtrate conduits 19, 20 are outwardly defined by a filtratinglayer 21, 22 respectively permeable to the filtrate.

The filter sector 6 comprises at least one element 23, 24 provided witha profiling forming the filtrate conduits 19, 20. The profiled element23, 24 forms itself the filtrating layer 21, 22 by means of that theprofiled element 23, 24 has a perforation permeable to the filtrate,i.e. that a plurality of openings or apertures 35 (FIG. 9) are arrangedin the profiled element. These openings or apertures may have differentforms dependent on the filtrating conditions. The openings or aperturesmay for example be round, oval, quadrangular, slot-formed, i.e.elongated etc.

The profiling of the element 23, 24 forms projections/recesses, which inthe illustrated embodiment have the character of ridges/valleys. Theseridges/valleys are elongated and are preferably, but not necessarily,orientated in parallel. The ridges/valleys may suitably form a crinkledor waved profiling. The ridges are in the figures denoted with 25 andthe valleys with 26. It may in this connection be pointed out that theexpression ridges/valleys should be interpreted in a wide way. Withinthe scope of this expression cases where it is suitable to describe thata single element is formed by extending ridges from a main plane as wellas cases where an element is formed with recessed valleys from a mainplane should be included.

The filter sector 6 has on its both sides profilings and they formfiltrate conduits 19, 20, which in direction towards the more narrow endof the filter sector intersectingly overlap each other, which clearlymay be seen in FIGS. 4-6 and 9. The filter sector 6 has on each of itsboth sides a profiled portion 27, forming a plurality of substantiallyparallel filtrate conduits 19, 20 respectively, which run from an outersector part respectively to an inner sector part, in which said filtrateconduits intersectingly overlap each other, and a substantially flatportion 28 corresponding to said outer sector part, said portion 28forming said filtrate conduits 19, 20 together with the profiling on theopposite side of the filter sector. The substantially flat portion 28 islikewise perforated on both opposite sides in order to form a filtratinglayer.

The filter sector 6 is formed by at least two at least partly profileddisc-like elements as the ones denoted 23 and 24, which are connected toeach other by way of a sandwich structure. It is thereby preferred thatboth elements 23, 24 of the filter sector are formed substantiallyequally. This is clearly shown in FIGS. 2 and 3, which show the filtersector from its both opposite sides.

It is suitable that the profiling on one of the sides of the filtersector 6 gives rise to filtrate conduits extending substantiallyparallel to one of the radially extending edges of the filter sectorwhile the profiling on the opposite side of the filter sector gives riseto filtrate conduits extending substantially parallel to the otherradially extending edge of the filter sector.

Due to the filtrating layer on both sides of the filter sector being atleast partly profiled, the active filter surface increases compared toprior art where the filter surfaces have always been flat. Thisincreases the capacity. As a consequence of that the profiling formsridges/valleys, the longitudinal direction of which runningsubstantially radially, these ridges/valleys will before and at thedelivery of the suspension in the container by the filter sectorcontribute to that the material filtered away from the filtrate is kepton both sides of the filter sector and brought up to the level of theremoval means 11. When flat filtrating layers are arranged on both sidesof the filter sector, there is a substantially bigger tendency thatmaterial filtered away falls off the filter sectors and back into thesuspension in the container.

It is preferred that the elements 23, 24 are formed by discs of metal orplastics. It should be noted that especially in the case of plastics asconstruction material, it would be possible to form the elements 23, 24of the filter sector so that they were made of only one piece ofmaterial.

When the elements 23, 24 are formed by two disc elements, it is suitablethat they are kept together by edge profiles 29 at their radial edges.These edge profiles may for example be arranged in a way that the edgeportions of the elements 23, 24, which are intended to be unperforated,extend into the edge profiles through a slot, which is provided inthese, in a way that is evident in FIG. 9. The edge profiles 29 therebysuitably grip around flat towards each other located edge portions ofthe elements 23, 24. The filter sector has also an edge-forming element30 at its periphery, said element 30 gripping around portions of thedisc elements 23, 24. The edge element 30 must therefore be formed withwaved contact surfaces towards the profiled portions 27 of the elements23, 24 in order to achieve tightness, while the edge element 30 may abutflatly towards the flat portions 28 of the disc elements 23, 24.

In a direction radially inwards the conduit section 7 adjoins sealinglyto the disc elements 23, 24 so that the filtrate conduits formed betweenthem are able to deposit the filtrate in the conduit section. Theconduit section 7 is for this purpose provided with axially definingwalls 44 (FIG. 8), which are suitably arranged in a waved configurationto the outside of the adjacent, perforated portions 27 of the discelements 23, 24.

FIG. 9 illustrates how the filter sector at one of its radial edges hasa specific connection element 31 provided in order to interact with anedge profile 29 of an adjacent filter sector to establish amale/female-like engagement, which can be fixed by latch means (notshown). The connection element 31 is here forming a female-like socket32 for reception of an edge profile 29 on an adjacent filter sector. Asomewhat different embodiment of the connection element 31 isillustrated in FIGS. 4 and 6, even if the same is still forming afemale-like socket.

It should be pointed out that the perforation of the disc elements 23,24, which have a rigid structure, i.e. is substantially different from aflexible filter cloth, may be realised by way of stamping, etching,laser cutting, etc.

This embodiment differs primarily from the previous by way of the filtersector having filtrate conduits forming profilings in the form ofridges/valleys over substantially the whole surface of both sides of thefilter sector. The filtrate conduits formed by the profiling on one sideof the filter sector extend substantially parallel to one radial edge ofthe filter sector, while the filtrate conduits formed by the profilingon the other side of the filter sector extend substantially parallel tothe other radial edge of the filter sector, while the filtrate conduitsthus will intersectingly overlap each other over substantially the wholesurface of both sides of the filter sector, which is obvious bycomparing FIGS. 10 and 11 and also FIG. 12.

It is in this embodiment suitable to form the elements 23, 24 so thatthey between each other form radially running conduits 33 at both radialedges of the filter sector, which conduits ensure that filtrate flowingin the filtrate conduits obliquely against the actual radial edge mayenter into the edge conduit 33 and in this be guided radially inwardsand be discharged in the conduit section 7 for further transport intothe rotor shaft 4 (FIG. 1). This function is according to the inventionachieved by that the elements 23, 24 at their radial edges are locatedwith a relative distance in the axial direction of the filter sector,wherein these edges may have a distance piece 34 between each other. Aconnection element 31 is as previously present at one of the edges ofthe filter sector, which for coupling of two adjacent filter sectors maybe arranged to engage with an edge forming distance piece 34 present atthe other edge of the filter sector, which is not shown in FIG. 12.

The filtration layer itself is also in this case formed by the profiledelements 23, 24 by means of the disc-like elements 23, 24 having aperforation of the type described in connection with the previousembodiment.

It should be noted that it is also possible to apply a disc 45 betweenthe profiled elements 23, 24 in order to obtain increased rigidity ofthe filter sector, which is shown in FIG. 12 with a dotted line. Thefiltrate conduits should in such a case be formed between each of theelements 23, 24 and the disc 45. The disc 45 could also be permeable tothe filtrate due to a suitable perforation in order to equalize betweenthe filtrate conduits. The disc 45 could however also be compact.

It should be noted that the elements 23, 24 may be relatively fixed on aplurality of positions over their surfaces, for example by means ofintermittent or continuous welding or gluing. The disc 45 may if presentbe included in the fixation.

It is evident that the described device is not limited to theexemplified embodiments. Thus, the device according to the invention maybe modified in several ways within the scope of the knowledge of theaverage man skilled in the art without deviating from the protectioncovered by the following claims. It should for example be noted that theprojections/recesses which are the result of that the profiling of theelement 23, 24 does not need to have the character of ridges/valleysextending along the whole or substantially the whole length of theelement. These ridges/valleys could instead be present intermittentalong the element in one of its dimensions. The element couldfurthermore have a further profiling, for example in the form ofridges/valleys in combination with the first mentioned in a theretoinclined, for example right-angled dimension in the main plane of theelement. The inventive profiling of the element 23, 24 is, in moregeneral terms, intended to be able to be realized with the aim of anyprojections/recesses as long as they lead to an increase of thefiltrating surface, which is achieved as a consequence of theperforation of the element and as long as the profiling is of the typethat it can give rise to filtrate conduits inside the perforated elementin order to carry away the filtrate. The projections/recesses could forexample be almost point-like, for example in the form of bulges, whichare distributed over the surface of the element. The nature of theprofiling, and also of the projections/recesses will of course bedependent on if the single element is intended to form the filtrateconduits by way of abutment to a plane disc or to another, also profiledelement. If the filtrate conduits are intended to be formed between aprofiled element and a plane disc, the profilings must of course beformed so that the filtrate is really able to flow from the radiallyoutermost portion of the filter sector and into the innermost filtratedischarging conduit section 7. If, however, two profiled elements areintended to be located directly towards each other or with anintermediate location of a perforated disc, it is enough that these twoprofiled elements interacting with each other may form such conduits forcarrying off filtrate, i.e. that the filtrate in that case might flowsuccessively in filtrate conduits formed as a consequence of theprofiling of one of the elements in order to thereafter flow towards theother profiled element and flow in the filtrate conduits formed in it,wherein in the case of an intermediate profiled disc, the filtrate wouldhave to flow through its more or less large openings. Thus, it isevident from the description, that the term "profiling" according to theelements 23 and 24 includes all such formings, which give rise to atopography of the element, which in a suitably chosen cross sectionincludes that it is possible to define projections or recesses or bothof them and particularly in such a way that filtrate conduits may arisebehind the perforated element, either as a consequence of the profilingof the single element or the profiling of this element in combinationwith the profiling of another element interacting with just saidelement. It is however always an advantage in the intended embodimentsaccording to the invention that the topography on the outwards directedsurfaces of the element, which topography is obtained as a consequenceof the profiling of the element, will be formed by rounded surfaces incombination with possibly plane surfaces, i.e. that the forming shouldbe such that mats of material filtered away, which are stuck on thefilter sector should easy fall off and not tend to remain in angles andcorners.

While the present invention has been described in accordance withpreferred compositions and embodiments, it is to be understood thatcertain substitutions and alterations may be made thereto withoutdeparting from the spirit and scope of the following claims.

We claim:
 1. A device in a filter sector for a rotating filter disc,comprising:a profiled filtrating element defining perforations beingpermeable to a filtrate; and a filtrate conduit defined by the profiledfiltrating element for carrying the filtrate resulting from filtrationthrough the profiled filtrating element to a narrow end of the filtersector for discharging the filtrate, the profiled filtrating elementbeing free from a filter cloth, the filter sector having a top side anda bottom side, a first filtrate conduit being defined by the top sideand a second filtrate conduit being defined by the bottom side, both thefirst and second filtrate conduits extending toward the narrow end andthe first filtrate conduit intersectingly overlapping the secondfiltrate conduit.
 2. The device according the claim 1 wherein theprofiled filtrating element has alternating projections and recessesdefined therein.
 3. The device according to claim 2 wherein theprojections are elongated ridges and the recesses are elongated valleys.4. The device according to claim 3 wherein the ridges and valleys form awaved profile.
 5. The device according to claim 3 wherein the ridges andvalleys form a crinkled profile.
 6. The device according to claim 2wherein the ridges have pointed tops that are distributed over theprofiled filtrating element.
 7. The device according to claim 1 whereinthe filter sector has profiled surfaces extending substantially overboth the top and bottom sides.
 8. The device according to claim 1wherein the top side has a profiled top portion and a substantially flattop portion and the bottom side has a profiled bottom portion and asubstantially flat bottom portion, the profiled top portion and thesubstantially bottom flat portion define a set of substantially paralleltop filtrate conduits, the profiled bottom portion and the substantiallytop flat portion define a set of substantially parallel bottom filtrateconduits, the top filtrate conduits intersect the bottom filtrateconduits, the top and bottom filtrate conduits extend from an outer partof the filter sector to an inner part of the filter sector.
 9. Thedevice according to claim 8 wherein the substantially flat top andbottom portions are perforated.
 10. The device according to claim 1wherein the filter sector is formed by a first partly profileddisc-shaped element and a second partly profiled disc-shaped elementthat are connected to one another.
 11. The device according to claim 10wherein a disc is disposed between the first partly profiled disc-shapedelement and the second partly profiled disc-shaped element, a set offiltrate conduits are defined between the disc and the first and secondpartly profiled disc-like elements.
 12. The device according to claim 10wherein the first partly profiled disc-shaped element abuts the seconddisc-shaped partly profiled element and filtrate conduits are definedtherebetween.
 13. The device according to claim 10 wherein the firstpartly profiled disc-shaped element is substantially equal to the secondpartly profiled disc-shaped element.